In my prior U.S. Pat. No. 3,882,852 granted Apr. 13, 1975, there is disclosed a device for dilating the uterus comprising a hollow rigid tube upon which an inflatable balloon is mounted in coaxial relation. The tube serves as a conduit-forming member for the introduction of an endoscope or other surgical instrument, and the balloon serves to dilate the uterine cavity so that the surgical procedure may be performed by structure disposed at the distal end of the tube element. So-called Foley catheters are also known in the art, and are used for dilation purposes. But owing to the absence of a rigid element, they do not have useful application in the field of gynecological surgery.